Generally, electric furnaces heat and melt metal or alloys using electric energy. In such an electric furnace, scraps are inserted into the furnace and then arc currents are applied between three electrodes and the scraps, thus heating the scraps to melt them.
Slag is formed on an upper surface of molten steel in the electric furnace by oxidation of impurities contained in the scraps.
The slag isolates the molten steel in the electric furnace from the air, thus retaining arc-generating heat, and preventing the molten steel from adsorbing impurities contained in the air.
The slag functions to enhance the power efficiency of the furnace and to improve the quality of the steel.